1. Field of the Invention
The present invention relates to the field of starter gearing in general and in particular to that portion of the field of starter gearing which relates to non-indexing positive shift dentil type overrunning clutch starter gearing.
2. Description of the Prior Art
Clutches of the general type described herein above are well known in the art, but the art teaches that such drives require rather complicated mechanisms to separate the dentils of the overrunning clutch. An example of such drive is illustrated in U.S. Pat. No. 3,263,509, by Digby, assigned to the assignee hereof. Such starter gearing mechanisms as illustrated in the above noted letters patent renders these drives suitable only for large engine installations, primarily large volume displacement diesel engines. A similar type of overrunning clutch suitable for smaller engine installations, i.e., engine installations requiring less than 70 lb. ft. of steady state torque during cranking, is illustrated in U.S. Pat. No. 3,714,834 by Digby, assigned to the assignee hereof. Initial development criteria of said smaller engine drive starters required the removing of the complicated dentil separation mechanism and reducing the drive in size in order to meet the objectives of suitability for smaller engine installations. However, such starter gearing suffered from a major defect, that is, the drive which was initially very reliable, eventually (within as little as one-fifth of its expected life) begins to suffer an impositiveness in engagement with the engine to be started. Initial examination of such drives has shown that a tooth abutment between the pinion gear and the gear of the engine to be started prevented engagement of the drive and allowed sufficient axial movement of the shifting mechanism for the starter motor contacts to be closed, thereby causing the power shaft to rotate. Such action occurring without the inter-engagement of the pinion and the ring gear of the engine resulted in tooth milling, either of the ring gear or of the pinion gear, which thereafter required expensive and time consuming replacement. To solve this initial problem, it was believed that the use of a bearing sleeve underneath the pinion gear, as well as a thrust bearing means interconnecting the pinion gear and starter gearing sleeve which couples the starter gearing to the rotary power shaft, would eliminate this problem. By providing an intermediate low friction member, or washer, between a high speed rotating pinion and a comparatively low speed rotating body (the bearing sleeve) the amount of rotary energy being transmitted from the pinion to the sleeve was minimized. However, the use of the bearing sleeve in conjunction with the thrust body restricted the use of a pinion gear size larger than the smallest sized pinion used on many of the small engine installations for this type of drive. Further, the interaction of the helical splines was such as to cause a severe axial load on the stop mounted to the power shaft, so as to result in some breakage of the shaft under these conditions. Also, the bearing sleeve had to be brazed to the body which is an expensive process and has caused problems such as breaking loose from the body to which it is brazed.